FIG. 4 schematically shows an example of a rotating electric machine such as a ring motor 1.
Ring motors 1 have a stator 2 and a rotor 3 rotating within it; the stator 2 and rotor 3 have large dimensions such that a tool to be activated by the motor 1 is at least partly within the rotor 3.
In this respect FIG. 5 shows a typical example of application of a ring motor to a mill (gearless mill).
The ring motor 1 is connected to and drives the mill 5 that is provided with a mouth 6 for introducing the material to be treated into it.
The stator 2 and the rotor 3 are well known to include windings 10 made of conductive bars 11 housed in slots of the stator 2 or rotor 3.
The conductive bars have straight parts 12 that are housed in the slots, and end windings 13 that are outside of the slots and are bent with respect to the straight parts 12; these end windings 13 have terminal portions 14 that are connected together to define the windings 10.
In addition, to electrically and mechanically protect the terminal portions 14, above the electrically connected terminal portions 14 an electric insulating material 15 and protective caps 16 are provided.
The motor 1 is housed within an airtight casing; this casing prevents the motor from being influenced and possibly damaged by external, environmental factors.
Nevertheless, in some cases, the airtight properties of the casing get lost; when this occurs environmental factors such as humidity, water, mud, dust can enter the casing, causing risks of damages to the electric machine.
In particular applications such as ring motors for mills, because of the environment where the ring motors have to operate, these risks can be particularly high.